System for dispensing liquid carbon dioxide



July 9, 1957 J. c. HEssoN 2,798,365

SYSTEM FOR DISPENSING LIQUID CARBON DIOXIDE Filed Sept. 27, 1955 5 Sheets-Sheet l -July 9, 1957 J, C, HESSON 2,798,365

SYSTEM FOR DISPENSING LIQUID CARBON DIOXIDE Filed sept. 27, 1955 s sheets-sheer 2 July 9, 1957 J. c. HEssoN 2,798,365

SYSTEM' FOR DISPENSING LIQUID CARBON DIOXIDE Filed Sept. 27. 1955 5 Shee1'.s-Shee' 3 SYSTEM FOR DISPENSING LIQUID CARBON DIOXIDE .lames C. Hesson, Riverdale, Ill., assignor to Cardox Corporation, Chicago, Ill., a corporation of Illinois Applicaon September 27, 1955, Serial No. 536,798

8 Claims. (Cl. 62-1) This invention relates to new and useful improvements in distribution systems for liquefied gases and deals more particularly with systems wherein liquid carbon dioxide is delivered from storage, where it is maintained at a low temperature and a corresponding low vapor pressure, to a point of use and the vapor formed during delivery is separated from the liquid and reliqueed at a suicient elevation for gravitational return to the flow path through which the liquid is delivered to the point of use.

It has been found that liquid carbon dioxide is an excellent medium for the low temperature refrigeration of cold test boxes, tumbling drums for removing ash materials from articles of molded rubber or the like, and other similar purposes. Difficulties have been encountered, however, in the economical distribution of the liquid carbon dioxide used for such purposes.

For example, a single storage container may be employed to supply low temperature and pressure liquid carbon dioxide to one or more remotely located points of use. The liquid carbon dioxide, therefore, must flow through a substantial length of pipe to reach its destination and, during such flow, a portion of the liquid will be unavoidably evaporated by the transfer of heat to the liquid from the surrounding atmosphere. Since the carbon dioxide vapor discharged with the liquid at a point of use has very little heat absorbing capacity, such vapor may be considered to be almost a complete loss. More specifically, a one-half inch pipe, having a normal thickness of insulation, lled With liquid carbon dioxide stored at a temperature of F., and exposed to an atmospheric temperature of 80 F. will absorb enough heat to evaporate from live to ten pounds of the liquid per hour for each one-hundred feet of pipe.

Recovery of the carbon dioxide Vapor which would be lost by its discharge at the point of use presents several problems. First, the cost of the recovery operation is limited by the value of the available carbon dioxide vapor. Further, impurities such as oil and water may be introduced vinto the liquid carbon dioxide by the use of lubricated equipment such as pumps and compressors and such impurities must be separated from the carbon dioxide. Additionally, the recovery system must operate efficiently despite wide variations in the quantity of available vapor.

It is the primary object of this invention to provide a system for separating and recovering the Vapor formed during the delivery of liquid carbon dioxide to a point of use, the vapor being reliquefied by refrigeration only.

A further important object of the invention is to provide a system for delivering liquid carbon dioxide through a ow path from a refrigerated storage container to a point of use, the vapor formed during the delivery being separated from the liquid, just prior to its arrival at the point of use, reliquetied and returned by gravitational flow to the ow path.

Other objects and advantages of the invention will be ited States Patent i lf -2 apparent during the course of the following description.

In the accompanying drawings forming a part of this specification and in which like reference characters are employed to designate like parts throughout the same,

Figure l is a schematic View of a liquid carbon dioxide distribution system embodying the invention,

Figure 2 is a transverse sectional View of the condenser employed in the system of Fig. 1,

Figure 3 is a longitudinal sectional view of the float operated valve employed in the system of Fig. l, and

Figure 4 is a schematic view of a modified form of liquid carbon dioxide distribution system embodying the invention.

In the drawings, wherein for the purpose of illustration are shown the preferred embodiments of the invention, and lirst particularly referring to Fig. 1, reference character 5 designates a storage container surrounded by suitable insulating material 6. The container 5 is charged with liquid carbon dioxide in any suitable manner and the temperature of the liquid is maintained at approximately 0 F. by the coils 7 of a conventional mechanical refrigeration system, not shown. At this low temperature, the vapor pressure of the liquid carbon dioxide Will be maintained at approximately two hundred and ninety pounds per square inch, gauge.

Leading from the bottom of the container 5 is a pipe 8 which provides a flow path for the liquid carbon dioxide withdrawn from the container. This pipe is surrounded by suitable insulating material 9 to minimize the absorption of heat by the cold liquid carbon dioxide. A manually operated valve 11 is provided adjacent the container 5 to control the discharge of the carbon dioxide.

The pipe 8 leads from the container 5 to one or more points of use of liquid carbon dioxide and just in advance of each of such points the pipe is connected to the inlet port 12 of a float valve 13 by an insulated branch pipe 14. During the flow of carbon dioxide from the container 5 to the tloat valve 13, through the pipe 8 and branch pipe 14, heat will be absorbed by the very cold liquid and will convert a portion to vapor. Also, there will be a reduction in the pressure on the liquid due to the release of liquid from the system and this reduction will contribute to the conversion to vapor of a portion of the carbon dioxide entering the float valve 13. Since the carbon dioxide vapor has a very low heat absorbing capacity, Ythe oat valve 13 is provided to separate the vapor from the liquid before the latter ilows through the outlet 15 and an insulated pipe 16 to the point of use 17 for the liquid.

lt is to be understood that liquid carbon dioxide may be employed at the point of use 17 in connection with any conventional cooling operation which does not form a part of this invention. The point of use 17, however, should be located at approximately the same elevation as that of the storage container 5 in the modification of the invention illustrated in Fig. l, for a reason that will be later described. A manually operated valve 18 is provided for the pipe 16 adjacent the point of user17 to control the discharge of the liquid.

Referring now to Fig. 3 for a detail description of the float valve 13 and the manner in which it functions to separate the carbon dioxide vapor from the liquid owing to the point of use 17, it will be noted that the mixture of liquid and vapor flowing through the pipe 14 enters the oat chamber 19 through the inlet port 12 at the top of the valve. After entering the chamber 19, the liquid and vapor will separate and the liquid will occupy the bottom portion of the chamber from which it may flow through the outlet port 15 into the pipe 16. The carbon dioxide vapor in the upper portion of the chamber 19 will accumulate in or be released from the chamber in accordance with the position of the iioat operated valve 21 arranged between the upper portion of the chamber 19 ,an'd the vapor outlet port 22. i i The valve 21 is provided with circumferentially spaced ,splines 23 which slidably engage the bore of the valve guide 24 to limit movement of the valve to an axial di- .rection. At the outer end of the valve 21 there is provided an apertured seat 25 and thevalve 21 is provided -with a conical seating surface 26 which is movable into engagement with the valve seat to close the aperture through the latter. Movement of the valve 21 away from the valve seat 25, on the other hand, will open the aperture through the valve seat so that vapor will flow be- `rtween the splines 23 to the vapor outlet port 22. At the inner end of the valve 18 there is provided an operating .stem 27 which is threadedly connected to the valve 21. Axial movement is imparted to the valve 21 tocontr'ol .the flow of vapor from the chamber 19 to the vapor outlet port 22 by an elongated float 28 which is positioned in Vthe chamber 19 and is mounted for pivotal movement `about the pin 29 which passes through the block 30 that is rigidly connected to the iloat stern 31. One end portion of the block 30 is pivotally connected to the valve stem .27 by a pin 32 and the opposite end portion of the block is provided with a lug 33 for engaging the adjustable stop 34 to limit the pivotal movement of the block about the pin 29. Of course, some lost motion must be provided at the pin 32 to permit pivotal movement of the ,block 30 to elect the straight line movement of the valve 21 in its guide 24.

It will be readily apparent that the float 28 will be raised and lowered in accordance with the level of the liquid in the bottom portion of the chamber 19 and that such movement of the oat will effect the pivotal movement of the rigidly connected block 30 about the pin 29 to open and close the valve 21. In other words, as the level of the liquid carbon dioxide in the chamber 19 rises, the float 28 will be moved upwardly to elfect pivotal movement of the block 30 in a clockwise direction, as illustrated in Fig. 2, and will cause the valve 21 to move toward the valve seat 25 so that the seating surface 26 will close the aperture through the valve seat. The flow of vapor yfrom the upper portion of the chamber 19 to the outlet port 22 will thereupon stop and vapor will accumulate in the upper portion of the chamber until the level of the lliquid is lowered. No liquid, therefore, will be permitted to escape through the vapor outlet port 22. f Conversely, when the level of the liquid carbon dioxide in the chamber 19 drops, the float 28 will be lowered and `the block 30 will be pivoted in a counterclockwise direction, as viewed in Fig. 2, to effect movement of the valve V21 away from the valve seat 25 so that the vapor will be free to flow from the upper portion of the chamber 19 between the splines 23 of the valve to the vapor outlet port 22. This discharge of vapor from the chamber 19 Vwill continute until the liquid level again rises a suicient amount to cause the float 28 to reclose the valve 21.

Referring once again to Fig. l, it will be seen that the carbon dioxide vapor owing from the float valve 13 through the vapor outlet port 22 will enter an insulated branch pipe 35 for flow into the vapor return pipe 36 which may be connected to one or more branch pipes 35 depending upon the number of points of use forl liquid carbon dioxide. Branch pipe 35 and vapor return pipe 36 provide a flow path for the vapor from the oat valve 13 to the inlet port 37 in the upper portion of the insulated condensing chamber 38. V

Arranged within the chamber 38 are the coils 39 of a conventional refrigerator unit which includes a compressor 41 that receives the expanded refrigerating medium from the coils 39 through the pipe 42, compresses the re- Vfrigerating medium and discharges it to thev condenser -43 through a pipe 44. The'refrigerating medium within the condenser 43 is liqueled and flows into a receiver 45 from which it is withdrawn through a pipe 46 to be expanded through the expansion valve 47 into the refrigerating coils 39. The compressor 41 is driven by an electric motor 48 which is supplied with electrical energy through power supply lines 49 and through a solenoid operated switch 51. v

The position of the switch 51 is controlled by energization of Va circuit including wires 52 and 53, the latter of which is connected through a switch 54 to a wire 55, as illustrated in Fig. 2. The wires 52 and S5 are connected to an electrical supply source so that operation of the switch 54 controls the energization of the circuit through the solenoid operated switch 51 associated with the motor 48. f

Connected to the outlet port 56, in the bottom portion of the condenser chamber 38, is a pipe 57 which extends downwardly to and is in open communication 'with the pipe 8 at a point adjacent the valve 11. An air vent 58 is provided in the upper portion of the condenser cham- Vber 38 and is normally closed by a valve 59 which is opened only to permit the escape of air from the system when the latter is put into operation.

Referring now to Fig. ,2 for a detail description of the arrangement and operation of the switch 54 to control operation of the motor 48, a vertically arranged pipe 61 has its upper and lower end portions connected to the pipes 36 and 57, respectively, by pipes 62 and 63. The pipe 61, therefore, will contain liquid carbon dioxide at the same level as that of the liquid in the condenser chamber 38. Extending downwardly through the top of the pipe 61 ,is a thermometer well 64 having a closed lower end por- .tion to completely seal the interior of the well from the liquid in the pipe 61. The switch 54 is arranged at the top of the well 64 and is provided with a temperature responsive element 65 which projects downwardly into the well for a sufficient distance to position the bulb 66 thereof at approximately the level of the bottom of the condenser chamber 38.

When the level of the liquid in the pipe 57 rises to .the bottom portion of the condenser chamber 38, the liquid will ilow through the pipe 63 and into surrounding relationship with the Well 6,4 in the pipe 61. Since the carbon dioxide vapor in the pipe 61 has a low heat absorbing capacity, the temperature of the vapor in the pipe will be appreciably higher than that of the liquid so that variations in the liquid level in the pipe 61 above and below the position of the bulb 66 will eiect a substantial change in the temperature at the location of the bulb. When the level of the liquid in the pipe 61 rises to a point at which the well 64 is surrounded by liquid at or above the level of the bulb 66, the temperature at the bulb 66 will decrease to a value at which the temperature responsive element 65 will cause the switch 54 to open and break the circuit through the wires, 53 and 55 to the solenoid operated switch 51. The switch 51 will thereupon open and the operation of the motor 48 will be stopped so that cooling of the vapor within the condenser chamber 38 by the coils 39 will be discontinued. The flow of liquid from the pipe 37 to the pipe 8 will thereafter cause the level of the liquid carbon dioxide in y the condenser chamber 38 and in the pipe 31 to be lowered to a point at which the well 64 will be surrounded by .carbon dioxide vapor at the level of the bulb 66, The carbon dioxide vapor in the pipe 61 will absorb sufcient heat through the pipe to cause its temperature to'rise Aand the bulb will 4respond to the increase in temperature 'by causing the switch 54 to be closed. The closed circuit through the wires 52, 53and 5S will thereupon close the switch 51 so that the motor 48 will bestarted and will 4effect operation of the compressor 41. The coils 39 in lthe condenser chamber 38 Willonce again be supplied ,with refrigerating medium to lower the temperature of the vapor in the condenser Vchamber and to liquefy a fsuftcient quantity of the vapor to return the liquid level to a point at which the switch 54 will again be opened and operation of the motor 48 discontinued.

To summarize the operation of the system illustrated in Fig. l, liquid carbon dioxide is withdrawn from the storage Vcontainer 5 at attemperature of approximately F. and a corresponding'vapor pressure of about two hundred and ninety pounds per `square inch, gauge. The

liquid flows through the pipe 8 to a `iloat valve 13 and a portion of the liquid will be evaporated by the absorption of heat. At thetloat valve 13, the vapor is separated from the liquid and the liquid is permitted to ilow through the pipe 16 to a point of use 17 while the vapor is released to the vapor return pipe.36 through the branch pipe 35. The vapor in the return pipe 36 flows to'an elevated condenser chamber 38 where it is reliqueiied by contact with the cooling coils 39. The liquefied vapor will accumulate in the bottom portion of the condenser chamber 38and flow into the pipe 57 for return to the pipe 8 at a point adjacent the valve 11 for return to the float valve 13.

It will be readily apparent that the pressure of the liquid in the pipe 57 mustbe equal to the pressure of the liquid in the pipe 8 at the point of intersection between the two pipes. Further, the eiective pressure head of the liquid in the pipe 57 is equal to the diierence in elevation between the level of the liquid in the pipe 57 and the point of intersection between the pipes 57 and 8, less the difference in elevation between the point of intersection of the pipes and the highest point in the ow path provided by the pipe 8. In order to prevent a vapor lock in the system, the effective-pressure head of the liquid in the pipe 57 shouldbe suflicient to Overcome the resistance to the ow of carbon dioxide through the pipe 8, float valve 13 and vapor return pipe 36. Since the condenser chamber 38 is arranged at a sutiicient elevation to provide the necessary eiective pressure head for the liquid in the pipe 57, the temperature and pressure within the condenser chamber must be maintained at a relatively constant value below that in'the storage container 5 to maintain the liquid in the pipe 57 at approximately the level of the condenser chamber.

Control` of the level of the liquid in the pipe 57 is provided by the switch 54 which is operated inaccordance with the level of the liquid in the pipe 61 which surrounds the well 64. When the level of the liquid in the pipe 61 falls below that of the bulb 66, the switch 54 is closed to actuate the solenoid operated valve 51 and to start operation of the motor 48 so that the cooling coil 39 will condense or liquefy more of the vapor in the chamber 38. When the level ofthe liquid in the pipe 61 rises above the `level of the bulb 66, the switch 54 is opened to open the switch 51 and stop the operation of the motor 48 so that no refrigerating medium `will flow through the coil 39. In this manner, the level of the liquid in the pipe 57 is maintained at approximately the level of the bottom of the condenser chamber 38, and the pressure of the vapor in the condenser chamber will always be maintained below that of the vapor released from the float valve 13 `so that vapor will iiow from the latter to the condenser chamber.

The system described above provides for the discharge of only liquid carbon dioxide to a point of use 17, the vapor delivered to the float valve 13 along with liquid to be discharged being separated, reliqueed and returned to the liquid delivery system by refrigeration of the vapor at a suicient elevation to cause the liquid resulting therefrom to flow under the inuence of gravity back to the liquid delivery stream.

Referring now to Fig. 4 for a detail description of the modication of the invention illustrated therein, it will be noted that this modiication includes a Storage container covered with insulating material 6 and refrigerated by coils 7, and a ow path from the storage container v5 to a point of use 17- through the valve 11, pipe 8 covered by insulating material 9, branch pipe 14, iioat valve 13, pipe 16 and valve 18, all of which are identical to the corresponding elements illustrated-in Fig. 1 and have been designated by the same reference characters throughout. It will be noted, however, that the point of use 17 illustratedin Fig. 4, is at an elevation above that of the storage container 5.

Vapor released through the outlet port 22 of the oat valve 13 enters an insulated pipe 67 for flow to a condenser chamber 38. The condenser chamber38 and the refrigerating unit associated therewith are identical in construction and operation to those of the modification of the invention illustrated in Fig. l and the same reference characters have been applied to corresponding parts thereof. The condenser chamber 38 of the modiiication of the invention`illustrated in Fig. 4, however, is positioned in the Vicinity of and at an elevation above that of the iloat valve 13. It will also be noted that a branch lineV 68 connects the insulated, pipe 67 to the vapor outlet ports 22 of any additional float valves 13 which may be employed at additional points of use 17 of liquid carbon dioxide.

The pipe 57 leading from the bottom portion of the condenser chamber 38 leads to a liquid carbon dioxide receiver 69 which is positioned below and closely adjacent to the condenser chamber. At the bottom portion of the liquid carbondioxide receiver 69 there is provided an outlet port 71 which is connected to an insulated pipe 72 leading from the port 71 to a point in the pipe 8 adjacent to the branch pipe 14.

The operation of the modification of the invention illustrated in Fig. 4 will be described in detail as follows:

When liquid carbon dioxideis released from the oat valve 13 through the pipe 16 to the point of use 17, the

lreduction in pressure within the iloat valve 13 will cause liquid carbon dioxide to be withdrawn from the storage container 5 and through the ow path provided by the pipe Y8 and branch pipe 14 to the oat valve. Since the float `valve 13 is positioned adjacent the point of use 17 at a location that is remote from the container 5 and at an elevation considerably above that of the container 5, a portion of the liquid withdrawn from the container will be evaporated by the absorption of heat through the insulation 9 surrounding the pipe 8 and by the reduction in pressure caused by the increase in the pressure head of the liquid at the oat valve. The vapor which enters the float valve 13 with the liquid carbon dioxide is separated from theliquid and released through the outlet port 22 of the float valve to the pipe 67 for ow into the upper portion of the condenser chamber 38. The vapor within the chamber 38 is liquetied by the refrigerating action of the coil 39 in accordance with the level of the liquid in the bottom of the chamber, as was described in connection with the modication of the invention illustrated in Fig. l. The liquid carbon dioxide receiver 69, therefore, is maintained completely iilled with liquid.

The temperature and vapor pressure of the liquid in the carbon dioxide receiver 69 and the bottom portion of the condenser chamber 3S may vary under dilerent conditions of operation. The iloat valve 13, for example, may be located at an elevation of forty feet above the storage container 5 and the condenser chamber 38 may be positioned ten feet above the level of the float valve 13. Under these assumed conditions, and with carbon dioxide flowing through the pipe 8, the head of liquid carbon dioxide in the bottom portion of the condenser chamber would 'be approximately fifty feet and the pressure within the chamber would be approximately twentytwo pounds per square inch below that within the storage container 5.

On the other hand, when the system is shut down or operation istemporarily suspended, the pipe 8 will tend to become filled with carbon dioxide vapor so that the Vpressure within the pipe 8 will approximate that within the storage container 5. Under these conditions, the head of'the liquid carbon dioxide in the bottom portion of the condenser -chamber 38 will be approximately ten feet and the pressure within the chamber will be approximately've pounds per square inch below that within the sa'raaaets and when the valve 18 is opened to discharge carbon dioxide to the point of use 17, liquid will ow from the supply of liquid carbon dioxide near the point of use while the vapor is being eliminated from the pipe 8 by the float valve.

It will be readily apparent that the system illustrated receiver to the float valve 13 and will provide a reserve 5 in Fig. 4 provides for the discharge liquid carbon dioxide 10 to a point of use which is elevated relative to the storage container 5, the discharged liquid being substantially free of vapor and the evaporated portion of the liquid being reliquetied and stored near the point of use for subsequent re-entry into the distribution system. i

It is to be understood that the forms of this invention herewith shown and described are to be taken as preferred examples of the same, and that various changes in the shape, size, and arrangement of parts may be resorted to without departing from the spirit of the invention or the scope of the subjoined claims.

Having thus described the invention, I claim:

l. Apparatus for delivering liquid carbon dioxide from a storage container at a low temperature and pressure to a point of use, comprising means forming a flow path from said storage container to Vsaid point of use, means in said ilow path adjacent said point of use for separating the vapor from the liquid carbon dioxide to be discharged at the point of use, a chamber arranged at a selected elevation above the highest point of said tlow path, means 30,

for conducting the vapor from said vapor separating means to said chamber, means providing a path for the gravitational ow of liquid from said chamber to said flow path, and refrigerating means for reducing the temperature and vapor pressure in said chamber to liquefy the vapor therein and to cause vapor to ilow through said conducting means, said chamber elevation providing a pressure head of liquid in said gravitational low path which exceeds the difference in vapor pressures of they ,40

liquid at the opposite ends thereof.

2. Apparatus for delivering liquid carbon dioxide from a storage container at a low temperature and pressure to a point of use, comprising means forming a ow path from said storage container to said point of use, means- Y.

in said flow path adjacent said point of use for separating the vapor from the liquid carbon dioxide to be discharged at the point of use, a chamber arranged at an elevation above the highest point of said flow path, means for conducting the vapor from said vapor separating means to said chamber, means for refrigerating said chamber to liquefy the vapor therein and to cause the vapor to flow through said conducting means, means for controlling the actuation of said refrigerating means to maintain the liquid in said chamber at a substantially constant temperature and vapor pressure in said insulated chamber vto liquefy the vapor therein and to cause vapor to ow ffromfsaid vapor outlet to said insulated chamber when theoutlet'isopened, and means forming a liquid ow path'from the bottom portion of said insulated chamber to the ow path between said storage container and said point of use, the elevation of said insulated chamber providing a pressure head of liquid in said liquid flow path which exceeds the difference in vapor pressures of the liquid at opposite ends thereof.

4. Apparatus for delivering liquid carbon dioxide from a storage container at a low temperature and pressure to a point of use, comprising means forming a ow path from the bottom' portion of said storage container to said point of use, a chamber in said flowy path adjacent said point of use, said chamber having a vapor outlet inv the upper portion thereof, float actuated valve means for opening and closing said vapor outlet in responseto changes in the liquid level in said chamber to prevent the tlow of liquid through said vapor outlet and to release the vvapor from said flow path, an insulated chamber arranged at an elevation above the highest point of said ow path, means forming a tow path from said vapor outlet to said insulated chamber, refrigerating means for reducing the temperature and vapor pressure in said insulated chamber to liquefy the vapor therein and to cause vapor to ilow from said vapor outlet to said insulated chamber when the outlet is opened, temperature responsive means arranged in heat exchange relationship with the liquid in said insulated chamber for response to variations in the level of the liquid to control the actuation of said refrigerating means and to maintain liquid in the chamber at a substantially constant level, and means forming a liquid flow path from the bottom 5 portion of said insulated chamber to the flow path between said storage container and said point of use, the elevation of said constant liquid level providing a pressure head of liquid in said liquid tiow path which exceeds thedierence in vapor pressures of the liquid at opposite ends thereof.

V 5. Apparatus for delivering liquid carbon dioxide from arstorage container at a low temperature and pressure to a point of use, comprising a supply pipe for conducting liquid carbon dioxide from the storage container,

) va chamber adjacent said point of use for receiving the liquid carbon dioxide from said supply pipe together with the vapor that is formed during the ilow through said pipe, said chamber having a liquid outlet inthe bottom portion thereof and a vapor outlet in the upper portion thereof, a float actuated valve for openingv and closing said vapor outlet in response to changes in the liquid level, and means providing a path for the gravitational ow of liquid from the bottom portion of said chamber to said first mentioned ow path, the elevation of said constant liquid level providing a pressure head of liquid in said gravitational How path which exceeds the diierence in vapor pressures of the liquid at the opposite ends thereof.

3. Apparatus for delivering liquid carbon dioxide from a storage container at a low temperature and pressure to a point of use, comprising means forming a ilow path from the bottom of said storage container to said point of use, a chamber in said flow path adjacent said point of use, said chamber having a vapor outlet in the upper portion thereof, oat actuated valve means for opening and closing said vapor outlet in response to changes in level in said chamber, said valve opening said vapor outlet when the liquid in the oat chamber drops to a given level below the vapor outlet, a pipe for conducting liquid from said liquid outlet to said point of use, an insulated chamber arranged at an elevation above the highest point of said supply pipe, a pipe leading from said vapor outlet to said insulated chamber, a refrigerating coil positioned in said insulated chamber for reducing the temperature and vapor pressure to liquefy the vapor therein and to causervaporrto ow from said vapor outlet to said insulated chamber when the outlet is opened, and

. a pipe leading from the bottom portion of said insulated chamber to said liquid supply pipe for the gravitational owof liquid `from the chamber'to the supply pipe, the

, elevation of said insulated chamber providing a pressure head of liquid in the pipebetween the chamber and the supply pipe which exceeds the dilerence in vapor presthe liquid level in said chamber to prevent the tlow of 0 liquid through said vapor outlet and to release the vapor from said ow path, an insulated chamber arranged at an elevation above the highest point of said flow path,

. means forming a flow path from said vapor outlet to said 5 insulated chamber, refrigerating means for reducing the sures of the liquid in said chamber and in said supply pipe.

Y 6. Apparatus for delivering liquid carbon dioxide from a storage container at a low temperature and pressure to aj pointfofuse, comprising an insulated supply pipe for conducting liquid carbon vdioxide from .the storage contailler, a Chamber adjacent thepoint of use for'receiving the liquid carbon dioxide from the supply pipe together with the vapor that is formed during ow through said pipe, said chamber having a liquid outlet in the bottom portion thereof and a vapor outlet in the upper portion thereof, a float actuated valve for opening and closing said vapor outlet in response to changes in the liquid level in said chamber, said valve opening said vapor outlet When the liquid in the chamber drops to a given level below the vapor outlet, an insulated pipe for conducting liquid from said liquid outlet to said point of use, an insulated chamber arranged at a level above said point of use, an insulated pipe leading from said vapor outlet to said insulated chamber, a refrigerator unit having its cooling coil positioned in said insulated chamber, a motor for driving said refrigerator unit to cause said cooling coil to liquefy the vapor in the insulated charnber, a temperature responsive switch for actuating said motor when the liquid in said insulated -chamber is lowered below a given level, and a pipe leading from the bottom portion of said insulated chamber to said supply pipe for the gravitational flow of liquid from the chamber to the supply pipe.

7. Apparatus for delivering liquid carbon dioxide from a storage container at a W temperature and pressure to a point of use at substantially the same elevation as that of the container, comprising means forming a flow path from said storage container to said point of use, means in said flow path adjacent said point of use for separating the vapor from the liquid carbon dioxide to be discharged at the point of use, a refrigerated chamber arranged at a level above that of said storage container, the point of use and the tlow path therebetween, means for conducting the vapor from said vapor separating means to said refrigerated chamber to liquefy the vapor, and means providing a path for the gravitational ilow of liquid from said refrigerated chamber to a point in said 110W path adjacent the storage container, the elevation of said refrigerated chamber being suiciently greater than that of the highest portion of said flow path to create a liquid carbon dioxide pressure head in the path of gravitational flow which exceeds the frictional resistance to the flow of carbon dioxide through said flow path, vapor separating means and vapor conducting means.

8. Apparatus for delivering liquid carbon dioxide from a storage container at a low temperature and pressure to a point of use at an elevation above that of said container, comprising means forming a flow path from said storage container to said elevated point of use, means in said ow path adjacent said point of use for separating the vapor from the liquid carbon dioxide to be discharged at the point of use, a chamber arranged at an elevation above said separating means, means for conducting the vapor from said separating means to said chamber, refrigerating means for reducing the temperature and Vapor pressure in said chamber to liquefy the vapor therein and to cause vapor to flow through said conducting means, and means providing a path for the gravitational tlow of liquid from said chamber to a point in said ilow path adjacent the separating means, the elevation of said chamber providing a pressure head of liquid in said gravitational W path which exceeds the difference in vapor pressures of the liquid at opposite ends thereof.

References Cited in the le of this patent UNITED STATES PATENTS 2,021,394 Wade Nov. 19, 1935 2,278,192 Cantacuzene Mar. 31, 1942 2,291,678 Benz et al. Aug. 4, 1942 2,341,698 Dennis Feb. 15, 1944 2,488,813 Garretson Nov. 22, 1949 2,496,185 Voss et al. Jan. 31, 1950 

1. APPARATUS FOR DELIVERING LIQUID CARBON DIOXIDE FROM A STORAGE CONTAINER AT A LOW TEMPERATURE AND PRESSURE TO A POINT OF USE, COMPRISING MEANS FORMING A FLOW PATH FROM SAID STORAGE CONTAINER TO SAID POINT OF USE, MEANS IN SAID FLOW PATH ADJACENT SAID POINT OF USE FOR SEPARATING THE VAPOR FROM THE LIQUID CARBON DIOXIDE TO BE DISCHARGED AT THE POINT OF USE, A CHAMBER ARRANGED AT A SELECTED ELEVATION ABOVE THE HIGHEST POINT OF SAID FLOW PATH, MEANS FOR CONDUCTING THE VAPOR FROM SAID VAPOR SEPARATING MEANS TO SAID CHAMBER, MEANS PROVIDING A PATH FOR THE GRAVITATIONAL FLOW OF LIQUID FROM SAID CHAMBER TO SAID FLOW PATH, AND REFRIGERATING MEANS FOR REDUCING THE TEMPERATURE AND VAPOR PRESSURE IN SAID CHAMBER TO LIQUEFY THE VAPOR THEREIN AND TO CAUSE VAPOR TO FLOW THROUGH SAID CONDUCTING MEANS, SAID CHAMBER ELEVATION PROVIDING A PRESSURE HEAD OF LIQUID IN SAID GRAVITAIONAL FLOW PATH WHICH EXCEEDS THE DIRRERENCE IN VAPOR PRESSURES OF THE LIQUID AT THE OPPOSITE ENDS THEREOF. 